code: def test_simple_hook(tmpdir):
      nb_file = str(tmpdir.join("notebook.ipynb"))
      md_file = str(tmpdir.join("notebook.md"))
      nbformat.write(
          new_notebook(cells=[new_markdown_cell("Some text")]), nb_file
      )
  
      nb = jupytext.read(nb_file)
      jupytext.write(nb, md_file)
  
      with open(md_file) as fp:
          text = fp.read()
  
      assert "Some text" in text.splitlines()
  
file_path: jupytext/tests/functional/others/test_read_write_functions.py
imports: from io import StringIO
  from pathlib import Path
  import nbformat
  from nbformat.v4.nbbase import new_markdown_cell, new_notebook
  import jupytext
  from jupytext.compare import compare, compare_notebooks
label_desc: Use image node_id 1 for calling a global function with example usage: test_simple_hook(tmpdir) without return types